The present invention concerns a machine for cutting stacked sheets of stock. The machine has a counter for accommodating the stock. The rear of the counter accommodates the stock to be cut and the front of the counter the cut stock. The rear of the counter also accommodates a mechanism for advancing the stack and a baffle for one side of the stack to rest against. A bent is positioned above the counter and accommodates a blade for cutting the stock and a holdfast that can be lowered onto the top of the stack. A control panel and a display panel are positioned on the front side.
A machine of the aforesaid genus is known from Europe Patent 0 056 974 A1 and German 19 637 027 A1. Such machines are employed to cut stacked sheets of in particular paper, cardboard, plastic, and similar stock. When in particular the sheets are to be assembled, the stack-advancing saddle must move into position in relation to the blade very precisely to ensure that the blade can cut the stack very precisely in relation to the specified line of separation. Even slight errors, deviations due to warping of the sheets for example, can deflect the blade from the intended line of separation. In assemblages in particular the incision can enter beyond the edges of the intended format. To prevent such malfunctions, the assembled sheets are held down fast such that the edges of the intended format are not directly adjacent but separated. This procedure of course necessarily leaves strips between the cut edges. Similarly, the edge contours of the stacks are trimmed before the stacks are cut. Once the edges have been cut, the stack being cut will be present in a well defined form or dimension, which decisively affects the precision of the subsequent main cutting processes.
In practice, it is very difficult for the operator to monitor the precise position of the stock being cut at the rear of the cutting surface. As the front of the counter empties, the operator must lean far over it to force the stack or stacks being cut against the stack-advancing mechanism or under the blade and aligns it or them against the abutment lateral baffle. The operator will often unnecessarily be compelled to repeat aligning operations due to his inability to see the rear of the counter and accordingly whether the stock has already been satisfactorily aligned or not.
The operator must be able to monitor various procedures at the rear of the stock-accommodating counter. When assembly sheets are being cut for example, the upper sheets in adjacent stacks can override the stack-advancing mechanism. Stacks can become displaced. Individual sheets can become displaced, by compressed air distorting the uppermost sheet for example. When in particular the sheets are not provided with cutting marks, it is almost impossible for the operator to monitor the rear of the counter because the individual sheets run into each other without visible reference marks.
The object of the present invention is accordingly an improved machine of the aforesaid genus that will allow the operator to precisely determine the position of the stock being cut, so that corrections will need to be made only when the stock is not resting precisely against the stack-advancing mechanism or abutment lateral baffle.
This object is attained in accordance with the present invention in a machine of the aforesaid genus by at least one camera at the rear of the stock-accommodating counter that monitors the position of the stock being cut in relation to the stack-advancing mechanism or lateral baffle, the image being displayed on the display in real time.
The machine in accordance with the present invention considerably improves not only operator ergonomics but also the quality of the cut. The operator will be able to easily carry out all requisite operations, mad corrections in the position of the stack will need to be made when errors at the rear of the stock-accommodating counter are displayed to the operator in real time. Only in this event will the operator need to intervene below the bent for example and correct the lateral position of the stack or stacks with a square or to align the stack or stacks with the square against the stack-advancing mechanism from the front. The indirect monitoring of the rear of the stock-accommodating counter with the camera, showing the real-time image on the display, will eliminate unnecessary interventions during the cutting process, considerably improving the accuracy of the cut and accelerating the process. Operator ergonomics will be essentially improved.
It is of advantage for the real-time image obtained by the camera at the rear of the stock-accommodating counter to be displayed only while the stack is being aligned in relation to the stack-advancing mechanism or lateral baffle. This approach will be of assistance to the operator in that the display of the real-time image will serve as a clue to monitor the position of the stack at the rear of the counter and intervene to correct it only when it needs to be corrected. The operator will be assisted even more if the image is displayed only when the stack is incorrectly positioned in relation to the stack-advancing mechanism or lateral baffle. The operator can then concentrate entirely on cutting the stock and on operating the machinery, the display indicating that the alignment is incorrect and that the position of the stack needs to be adjusted in relation to the stack-advancing mechanism or lateral baffle. One particular feature of the machine in accordance with the present invention is that it is impossible to initiate a cut with the blade while the stack is incorrectly positioned in relation to the stack-advancing mechanism or lateral baffle. The operator will accordingly be able to make a cut with the machine only when the stack is correctly positioned in relation to the stack-advancing mechanism or lateral baffle. This feature contributes considerably to the quality of the finished product.
It is basically possible to provide a separate screen to display the real-time image. Still, the display in one preferred embodiment displays graphical symbols representing various machine and operation routines, and the image can be superimposed onto it. The symbols can be partly or entirely replaced by the real-time image in this event. If the image replaces only some of the symbols, the rest of the display can simultaneously display the most important routines.
The operator will accordingly in accordance with the present invention be able to view a real-time image of the situation at the rear of the stack-supporting surface, and in a vicinity of the display panel that is particularly easy for him to see, facilitating corrections and allowing him to monitor the precise alignment of the stack in relation to the stack-advancing mechanism and lateral baffle.
The method of monitoring the rear of the stock-accommodating counter can be engineered in many different ways. Preferably, however, there will be several monitoring cameras distributed over the width of the counter.
It will be of advantage for the areas monitored by the monitoring cameras to overlap, each individual camera monitoring one strip of the rear of the stock-accommodating counter extending in relation to the direction the stacks are advanced in. The images can be displayed separately or composite. Each camera can for example be mounted on the stack-advancing mechanism and travel in relation to with it. Such an approach is of particular advantage when the precise alignment of the stack must be monitored against in relation to the stack-advancing mechanism. Mounting a particular camera stationary in relation to the rear of the stock-accommodating counter is also conceivable, in which case it will monitor a specific area of the counter. This approach can be a particular advantage when it is the position of the stack in relation to the lateral baffle that is being monitored. The camera or cameras can monitor the rear of the stock-accommodating counter from above or from the side or both. It is also conceivable to position the camera or cameras such that they can travel back and forth in relation to the rear of the stock-accommodating counter. This approach will make it possible to monitor the position of the stack in relation to both the stack-advancing mechanism and the lateral baffle with only one camera.
The monitoring camera or cameras in one particular embodiment of the present invention can monitor the stack between the stack-advancing mechanism and a lateral baffle from behind. The camera""s or cameras"" mount will in this event extend substantially horizontally. This approach will allow reliable monitoring even when the uppermost sheet in the stack rests correctly against, the stack-advancing mechanism and the lateral baffle although the other sheets in the stack do not. The camera can in this event be able to cover the rear of the stack as well, covering the rear of the stock-accommodating counter through the gap between the stack advancing mechanism and the baffle.
A particularly sensible feature of the present invention is that the monitoring camera or cameras can pivot. Such a camera can for example pivot out of a vertical axis of observation wherein it can monitor a stack from above, and into a horizontal axis of observation, wherein it can monitor the rear of the stack from behind. This feature is particularly easy to incorporate by mounting the camera in an upright that can be pivoted by a motor, especially 90xc2x0.
Due to the optionally variable distance between the monitoring camera and the object being monitored, the particular area of interest of the stock being cut, that is, the camera should be provided with a variable-focus lens. A zoom lens will allow the operator to display the monitored area in the form of a magnified or reduced real-time image.
The aforesaid display of the real-time image only in the event of incorrect alignment of the stack in relation to the stack-advancing mechanism or lateral baffle is attained in accordance with a preferred advanced embodiment of the present invention in that the monitoring camera is connected to an image processor that can detect the position of the stock in relation to the stack-advancing mechanism or lateral baffle. Such image processors are state-of-the-art and allow very precise edge discrimination. When an edge of the stack does not coincide with its prescribed position against the stack advancing mechanism or lateral baffle, the image processor will detect the error and forward the information to the machine""s display system for display in relation to with the real-time image. Once the situation has been corrected and the stock being. cut rests precisely against the stack advancing mechanism or lateral baffle, the processor will detect the correction and eliminate the real-time image from the display. Further-characteristics of the present invention will now be specified with respect to the accompanying drawing, all specific characteristics and combinations thereof being essential to the invention.